The purpose of the research is to investigate the structure of plasma lipoproteins -- specifically those of the very low density (VLDL), intermediate density (IDL) and low density (LDL) classes. Of particular interest are the lipid constituents; lipid dynamics is assessed by Carbon-13 and Phosphorus-31 nuclear magnetic resonance spectrometry. The structure of lipoproteins isolated from humans is contrasted with that of lipoproteins from normal and cholesterol-fed rabbits and with that of lipids in atherosclerotic plaques isolated from cholesterol-fed rabbits. Recently, attention has focused on the role of VLDL structure in the catabolism of VLDL to IDL (VLDL-remnants) to LDL, a sequence which is contingent on the activity of lipoprotein lipase which catalyzes the hydrolysis of VLDL triglycerides. To this end, lipoproteins purified from guinea pigs are utilized.